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Flashcards in Lesson 3 Review Deck (18)
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0
Q

SEER is the measure of a heat pumps____. It is expressed in___

A

Cooling efficiency; Btu/Watt

1
Q

What is Refrigeration?

A

The process of transferring heat energy from the area it is not wanted to an area it won’t make a difference.

2
Q

The typical compression ratio for a heat pump operating in cooling mode is approximately?

A

3:1

3
Q

What is the coefficient of performance (COP) of a heat pump?

A

How much heat the heat pump is producing compared to and electric furnace using the same amount of electricity.

4
Q

A heat pump thermostat is set so that there will be a deadband range of about ___ deg. F between the heating & cooling cycles, A closer setting might result in ___

A

2 to 4 degrees F ; frequent cycling

5
Q

A typical reversing valve cylinder with 3 tubes on one side and a single tube on the other side. The center tube of the three is always the compressor ___ connection. The single tube on the opposite side of the cylinder is always the compressor ___ connection.

A

suction, discharge

6
Q

At what liquid line temperature does a temperature-activated defrost control typically terminate the defrost cycle?

A

50 to 65 deg. F

7
Q

At what head pressure does a pressure-activated defrost control typically terminate the defrost cycle?

A

250 to 300 psig

8
Q

Why does a heat pump require three-function control?

A

because a H.P. provides 3 functions: heating, cooling and defrosting the outdoor coil of ice build up

9
Q

What is meant by excessive supplemental heat?

A

More heat than would be required to neutralize the cooling effect that occurs during the defrost cycle

10
Q

What is the “critical point” of refrigerant?

A

The maximum saturation condition at which evaporation and condensation may occur

11
Q

The physical properties of a refrigerant may be represented as a curve on a pressure-enthalpy diagram. Plots points that fall outside and to the right of curve indicate that refrigerant is a ___. Plot points that fall outside and to the left indicate that the refrigerant is an ___. Plot points that fall inside the curve itself indicate that the refrigerant is a ___.

A

Superheated vapor, subcooled liquid, mixture of saturated liquid and vapor

12
Q

One of the most important principles of refrigeration is that an increase in pressure on a liquid results in an ___ in the liquids boiling temperature.

A

Increase

13
Q

In the cooling mode, which coil (indoor or outdoor) of a heat pump system functions as a condenser? Which coil during the heating mode?

A

In the cooling mode, the outdoor coil functions as the condenser. In the heating mode, the indoor coil functions as the condenser.

14
Q

What is meant by referring to a vapor compression system as a “closed” system?

A

The term “closed” means the system continually repeats itself without depleting the refrigerant contained within it.

15
Q

Why are suction-line accumulators and crankcase heaters often required to protect heat pump compressors?

A

liquid refrigerant can build up in the crankcase during the off-cycle which causes poor lubrication on start up and increases bearing wear.

16
Q

Why is the indoor air volume required for heat pump operation greater than the volume required for cooling only applications?

A

To ensure adequate condensing of the refrigerant during the heating mode.

17
Q

Why does the indoor coil of a heat pump need more area than the indoor coil of a cooling only unit?

A

To prevent the condensing temperatures and corresponding head pressures from becoming to high during the heating cycle